expand_unop can expand narrow clz, clrsb, ctz, bswap, parity and
ffs operations using optabs for wider modes.  These expansions
apply only to scalar integer modes (and not for example to vectors),
so the patch adds explicit checks for that.

2017-08-30  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* optabs.c (widen_leading): Change the type of the mode argument
	to scalar_int_mode.  Use opt_scalar_int_mode for the mode iterator.
	(widen_bswap): Likewise.
	(expand_parity): Likewise.
	(expand_ctz): Change the type of the mode argument to scalar_int_mode.
	(expand_ffs): Likewise.
	(epand_unop): Check for scalar integer modes before calling the
	above routines.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>

From-SVN: r251506